This invention relates to a process for making a nonwoven fabric including the steps of melt-extruding thermoplastic synthetic resin fiber and then thinning the fiber by stretching this fiber under hot air blast. This invention relates also to an apparatus used for this process.
It is well known to feed continuous fibers of melt blown thermoplastic synthetic resin onto a conveyor belt and thereby to form a nonwoven fabric. According to this well known process, a melt-extruder is provided with a plurality of nozzles arranged in an array adapted to discharge continuous fibers which are stretched and thinned under hot air blast in molten or semi-molten state.
In the case of the well known process, the continuous fibers extending parallel one to another in an orderly manner immediately after discharged from the nozzles may be deflected under the effect of the hot air blast and fused one with another in molten or semi-molten state before these continuous fibers reach the conveyor belt. Consequently, a plurality of fibers may be bundled together and/or a plurality of fibers may be intertwined together to form a fibrous lump as the fibers are cooled Such fibrous bundles and/or lumps necessarily result in the nonwoven fabric presenting uneven fiber distribution, rough touch and more or less spotted appearance. While such defects of the nonwoven fabric are not remarkable so far as the nonwoven fabric is of component fibers each having a diameter less than 3 xcexcm, such defects can no more neglected and its functional value as well as its commercial value will correspondingly go down if the fiber diameter is as large as in order of 10xcx9c20 xcexcm.
It is an object of this invention to provide a process and an apparatus enabling a nonwoven fabric to be made without an anxiety-of forming bundles and/or lumps of continuous component fibers even if each of these component fibers has a relatively large diameter.
According to a first aspect of this invention, there is provided a novel process for making a nonwoven fabric and, according to a second aspect of this invention, there is a novel apparatus used to exploit the novel process.
Specifically, according to the first aspect of this invention, there is a process for making a nonwoven fabric comprising the steps of stretching and thereby thinning continuous fibers of thermoplastic synthetic resin discharged from a melt-extruder under hot air blast and then placing these continuous fibers upon conveyor means.
The process further comprises, there being provided a guide box located between the extruder and the conveyor means, the guide box having an upper end opening spaced apart from nozzles of the extruder by a predetermined distance and adapted to receive the stretched and thinned continuous fibers and a lower end opening formed adjacent the conveyor means and having a width larger than the upper end opening as viewed in a travelling direction of the conveyor means and suction means located under the conveyor means so as to in opposition to the guide box, the steps of putting the stretched and thinned continuous-fibers in order within the guide box so that the stretched and thinned continuous fibers flow in well ordered manner from the upper end opening toward the lower end opening, then secondarily further stretching, thinning, cooling the continuous fibers at a flow velocity of the fibers maintained or increased in vicinity of the upper end opening, and placing the continuous fibers upon the conveyor means.
According to the second aspect of this invention, there is provided an apparatus adapted to stretch and thereby to thin continuous fibers of thermoplastic synthetic resin discharged from a melt-extruder under hot air blast and then to place these continuous fibers upon conveyor means, the apparatus comprising a guide box located between the extruder and the conveyor means, the guide box having an upper end opening spaced apart from nozzles of the extruder by a predetermined distance and adapted to receive the stretched and thinned continuous fibers and a lower end opening formed adjacent the conveyor means and having a width larger than the upper end opening as viewed in a travelling direction of the conveyor means and suction means located below the conveyor means so as to be opposed to the guide box with the conveyor means therebetween, the suction means being capable of putting the continuous fibers in order, the continuous fibers being subjected to the hot air blast and then secondarily further stretching, thinning and cooling the continuous fibers by maintaining or accelerating a flow velocity of the continuous fibers in vicinity of the upper end opening.
The apparatus and the process according to this invention for making the nonwoven fabric enable the continuous fibers discharged from the melt-extruder to be introduced into the guide box in the well ordered condition substantially similar to the condition in which the continuous fibers have been discharged. In addition, the apparatus and the process according to this invention enable the velocity of the continuous fibers immediately after discharged to be maintained or increased so that the continuous fibers may be effectively stretched and thereby thinned while they are gradually cooled. In this way, this invention provides the nonwoven fabric free from any bundle and/or clump of the fibers and offering a comfortable touch.